Note that while the download page and tools don't perform license checks, you are supposed to have a visual studio license to use that package[1]. It is intended as an easy way for VS customers to install tools on build machines and the like without doing a full VS install, not a way for non-customers to get a free compiler. Individuals can get a free license to VS community that would include this package[2], but commercial use requires a paid license.
[1] https://visualstudio.microsoft.com/downloads/#build-tools-fo...
[2] https://visualstudio.microsoft.com/vs/community/